This invention relates, in general, to oscillators operating at microwave frequencies, and more particularly to miniature oscillators which are mechanically tunable over wide bands of microwave frequencies and which maintain a high degree of frequency stability over changes in temperature.
Often, microwave oscillators utilize cavities for resonant frequency determinants. Prior art cavity oscillators generally have relatively high Q (series resonant quality factor) values and are often temperature compensated. However, since the active elements of these oscillators are often an integral part of the cavity, the oscillators are relatively large. Frequently the frequency output of such oscillators is small, on the order of 1.5 GH.sub.z, and expensive multipliers are required to increase the output to the desired frequency Space limitations have been a major detriment to the use of such cavity oscillators.
Some oscillators have been designed with space limitations in mind, such as microstrip oscillators and microstrip oscillators with dielectrics. Although microstrip oscillators with dielectrics have high Q values, they are incapable of mechanical tuning over a wide tuning range. Microstrip oscillators without dielectrics have low Q values as well as limited tuning ranges.
Attempts within the prior art to develope a miniature wide range mechanically tuned microwave oscillator with high Q values capable of maintaining frequency stability over changes in temperature have been unsuccessful. Oscillators designed for frequencies below the microwave range incorporate crystals as the resonant frequency determining element in order to obtain the above specifications. However, crystals do not operate at microwave frequencies, and the prior art has not provided a substitute therefor.